Golf ball with vapor barrier layer and method of making same

ABSTRACT

A method of casting a portion of a golf ball comprising the steps of providing a single component that is blocked and stable at a first predetermined temperature and becomes unblocked at a second predetermined temperature, wherein said second predetermined temperature is higher than the first predetermined temperature; and reacting said single component at the second predetermined temperature to form the surrounding layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of co-pending U.S. applicationSer. No. 09/973,342, filed Oct. 9, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to a novel structure for a golfball, and more particularly to a golf ball with a moisture vapor barrierlayer.

BACKGROUND OF THE INVENTION

[0003] Solid core golf balls are well known in the art. Typically, thecore is made from polybutadiene rubber material, which provides theprimary source of resiliency for the golf ball. U.S. Pat. Nos. 3,241,834and 3,313,545 disclose the early work in polybutadiene chemistry. It isalso known in the art that increasing the cross-link density ofpolybutadiene can increase the resiliency of the core. The core istypically protected by a cover from repeated impacts from the golfclubs. The golf ball may comprise additional layers, which can be anouter core or an inner cover layer. One or more of these additionallayers may be a wound layer of stretched elastic windings to increasethe ball's resiliency.

[0004] A known drawback of polybutadiene cores cross-linked withperoxide and/or zinc diacrylate is that this material is adverselyaffected by moisture. Water moisture vapor reduces the resiliency of thecores and degrades its properties. A polybutadiene core will absorbwater and loose its resilience. Thus, these cores must be coveredquickly to maintain optimum ball properties. The cover is typically madefrom ionomer resins, balata, and urethane, among other materials. Theionomer covers, particularly the harder ionomers, offer some protectionagainst the penetration of water vapor. However, it is more difficult tocontrol or impart spin to balls with hard covers. Conventional urethanecovers, on the other hand, while providing better ball control, offerless resistance to water vapor than ionomer covers.

[0005] Prolonged exposure to high humidity and elevated temperature maybe sufficient to allow water vapor to invade the cores of somecommercially available golf balls. For example at 110° F. and 90%humidity for a sixty day period, significant amounts of moisture enterthe cores and reduce the initial velocity of the balls by 1.8 ft/s to4.0 ft/s or greater. The change in compression may vary from 5 PGA toabout 10 PGA or greater. The absorbed water vapor also reduces thecoefficient of restitution (COR) of the ball.

[0006] Several prior patents have addressed the water vapor absorptionproblem. U.S. Pat. No. 5,820,488 discloses a golf ball with a solidinner core, an outer core and a water vapor barrier layer disposedtherebetween. The water vapor barrier layer preferably has a water vaportransmission rate lower than that of the cover layer. The water vaporbarrier layer can be a polyvinylidene chloride (PVDC) layer. It can alsobe formed by an in situ reaction between a barrier-forming material andthe outer surface of the core. Alternatively, the water vapor barrierlayer can be a vermiculite layer. U.S. Pat. Nos. 5,885,172 and 6,132,324disclose, among other things, a golf ball with a polybutadiene or woundcore with an ionomer resin inner cover and a relatively soft outercover. The hard ionomer inner cover offers some resistance to watervapor penetration and the soft outer cover provides the desirable ballcontrol. It is also desirable to minimize the water barrier layer suchthat other properties of the ball are unaffected. Additionally, U.S.Pat. No. 5,875,891 discloses an impermeable packaging for golf balls.The impermeable packaging acts as a moisture barrier limiting moistureabsorption by golf balls during storage.

[0007] However, there remains a need for other golf balls with animproved water vapor barrier layer and improved methods for applying awater vapor barrier layer on to the core of the golf ball.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to a golf ball comprising athin film of moisture vapor barrier with a moisture vapor transmissionrate preferably lower than that of the cover and more preferably lessthan or equal to that of an ionomer resin. The moisture vapor barriermay also comprise nano particles, flaked-metals, such as mica, ironoxide and aluminum, or ceramic particles disposed in the film to resistthe transmission of moisture into the core.

[0009] The present invention is also directed to a golf ball comprisinga soft, high specific gravity layer. Preferably, this layer also has alow moisture vapor transmission rate to decrease the amount of moisturepenetrating into the core of the golf ball. The high specific gravitylayer advantageously contributes to a high moment of inertia, low spinball.

[0010] The present invention is also directed to a golf ball comprisinga moisture vapor barrier, which can be a multi-layer thermoplastic film,a blend comprising ionomers, polyvinyl alcohol copolymer and polyamides,or a dispersion of acid salts of polyetheramines.

[0011] In accordance to another aspect of the invention, the moisturevapor barrier can be an intermediate layer, an inner cover layer, anouter core layer, a core coating or an outer cover coating.

[0012] The present invention is also directed to a golf ball having amoisture vapor barrier layer with a solid core and intermediate woundlayer(s). The moisture vapor barrier layer is preferably applied to awound layer and penetrates into the interstitial spaces in the woundlayer(s) to minimize the transmission of moisture vapor to theintermediate wound layer(s) and to the core. Each of the wound layers ispreferably made up of a material that is chemically, mechanically andphysically different than an adjacent wound layer.

[0013] The present invention is also directed to a golf ball having athin moisture vapor barrier layer with a thin thermoset urethane cover.Alternatively, the cover layer may be a relatively thick layer. Thethick cover allows more spin, feel, control and playability forgreenside play.

[0014] The present invention is also directed to a method of making agolf ball with a moisture vapor barrier layer. In accordance to oneaspect of the present invention, any layer of the golf ball can be madeby a single component casting method. Preferably, this single componentcasting method utilizes uretdione or isocyanate blocked materials, andis, therefore, stable at a predetermined low temperature. However, thismaterial becomes deblocked at a predetermined elevated temperature andreacts to form the moisture vapor barrier layer or other components ofthe ball.

[0015] In accordance to another aspect of the invention, the thinmoisture vapor barrier layer can also be manufactured by a two-componentcastable system. Preferably, two distinct castable components are mixedand react with each other prior to casting to form the moisture vaporbarrier layer. The moisture vapor barrier layer may also be formed byspraying, dipping, preformed semi-cured shells, compression molding ofsheet stock, injection molding, reaction injection molding or othermethods.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the accompanying drawings which form a part of thespecification and are to be read in conjunction therewith and in whichlike reference numerals are used to indicate like parts in the variousviews:

[0017]FIG. 1 is a front view of a dimpled golf ball in accordance to thepresent invention;

[0018]FIG. 2 is a cross-sectional view of the golf ball in FIG. 1showing a solid core surrounded by a thin moisture vapor barrier layerand a cover;

[0019]FIG. 3 is a cross-sectional view of another golf ball inaccordance to the present invention showing a solid core with multiplewound layers surrounded by a thin moisture vapor barrier layer;

[0020]FIG. 4 is a cross-sectional view of another golf ball inaccordance to the present invention showing a solid core with multiplewound layers surrounded by a thin moisture vapor barrier layer and adual layer cover;

[0021]FIG. 5 is a cross-sectional view of another golf ball inaccordance to the present invention a fluid filled core with multiplewound layers surrounded by at least one thin moisture vapor barrierlayer and a cover; and

[0022]FIG. 6 is a cross-sectional view of another golf ball inaccordance to the present invention showing a solid core surrounded bymultiple wound or unwound intermediate layers, each intermediate layerbeing surrounded by a thin moisture vapor barrier layer.

DETAILED DESCRIPTION OF THE INVENTION

[0023] As shown generally in FIGS. 1 and 2, where like numbers designatelike parts, reference number 10 broadly designates a golf ball inaccordance to the present invention. Golf ball 10 preferably has a solidcore 12, an intermediate layer 14 and a cover 16. Solid core 12 maycomprise a single spherical element, or it may comprise a core sphericalelement with one or more intermediate layers surrounding the sphericalelement. Solid core 12 can be made from any suitable core materialsincluding thermoset plastics, such as natural rubber, polybutadiene(PBD), polyisoprene, styrene-butadiene or styrene-propylene-dienerubber, and thermoplastics such as ionomer resins, polyamides,polyesters, or a thermoplastic elastomer. Suitable thermoplasticelastomers include Pebax®, Hytrel®, thermoplastic urethane, and Kraton®,which are commercially available from Elf-Atochem, E. I. Du Pont deNemours and Company, various manufacturers, and Shell Chemical Company,respectively. The core materials can also be formed from a castablematerial. Suitable castable materials include those comprising aurethane, polyurea, epoxy, silicone, IPN's, etc.

[0024] Additionally, suitable core materials may also include a reactioninjection molded polyurethane or polyurea, including those versionsreferred to as nucleated, where a gas, typically nitrogen, isessentially whipped into at least one component of the polyurethane,typically, the pre-polymer, prior to component injection into a closedmold where essentially full reaction takes place resulting in a curedpolymer having reduced specific gravity. These materials are referred toas reaction injection molded (RIM) materials.

[0025] Cover 16 is preferably tough, cut-resistant, and selected fromconventional materials used as golf ball covers based on the desiredperformance characteristics. The cover may comprise one or more layers.Suitable cover materials include ionomer resins, such as Surlyn®available from DuPont, blends of ionomer resins, thermoplastic orthermoset urethane, acrylic acid, methacrylic acid, thermoplastic rubberpolymers consisting of block copolymers in which the elastomericmidblock of the molecule is an unsaturated rubber or a saturated olefinrubber, e.g., Kraton® rubbers available from Shell Chemical Co.,polyethylene, and synthetic or natural vulcanized rubber such as balata.

[0026] Additionally, other suitable core and cover materials aredisclosed in U.S. Pat. No. 5,919,100 and international publications WO00/23519 and WO 01/29129. These disclosures are incorporated byreference in their entirety. Preferably, core 12 is made from apolybutadiene rubber material and cover 16 is made from a compositioncomprising a thermoset or thermoplastic urethane or a compositioncomprising an ionomer resin.

[0027] To prevent or minimize the penetration of moisture, typicallywater vapor, into core 12 of golf ball 10, intermediate layer 14 is amoisture vapor barrier layer preferably disposed immediately around core12. Preferably, moisture vapor barrier layer 14 has a moisture vaportransmission rate that is lower than that of the cover, and morepreferably less than the moisture vapor transmission rate of an ionomerresin such as Surlyn®, which is in the range of about 0.45 to about 0.95grams·mm/m²·day. The moisture vapor transmission rate is defined as themass of moisture vapor that diffuses into a material of a giventhickness per unit area per unit time. The preferred standards ofmeasuring the moisture vapor transmission rate include ASTM F1249-90entitled “Standard Test Method for Water Vapor Transmission Rate ThroughPlastic Film and Sheeting Using a Modulated Infrared Sensor,” and ASTMF372-99 entitled “Standard Test Method for Water Vapor Transmission Rateof Flexible Barrier Materials Using an Infrared Detection Technique,”among others.

[0028] In accordance to an aspect of the invention, moisture vaporbarrier layer 14 also has micro particles disposed therein. Theseparticles are preferably hydrophobic and create a more tortuous pathacross the moisture vapor barrier layer 14 to reduce the moisturetransmission rate of the layer 14. The micro particles may include nanoparticles, ceramic particles, flaked glass, and flaked metals (e.g.,micaceous materials, iron oxide or aluminum).

[0029] In accordance to an embodiment of the invention, the moisturevapor barrier layer 14 is a thin and soft rubber layer. Layer 14preferably has a specific gravity that is significantly higher than thespecific gravity of core 12 to produce a high moment of inertia ballwith a low rate of moisture vapor transmission. An exemplary materialfor layer 14 contains polybutadiene, a cross-linking agent, a freeradical source and high specific gravity fillers. An example of suchpolybutadiene-based material is as follows:

[0030] 100 parts polybutadiene polymer,

[0031] 5-10 parts metal acrylate or methacrylate cross-linking agent,

[0032] 5 parts zinc oxide as the density modifying material,

[0033] 2 parts dicumyl peroxide as the free radical source, and

[0034] X part(s) metal powder filler, such as tungsten or other heavymetals,

[0035] where X depends on the desired specific gravity of the batch andwhere X is a number, including integers and real numbers. Alternatively,butyl-based or natural rubbers are also suitable primary ingredients,due to their low moisture vapor transmission rates. A preferred metalacrylate is zinc diacrylate. Other suitable primary ingredients include,but are not limited to, trans polyisoprene, neoprene, chlorinatedpolyethylene, balata, acrylics, etc.

[0036] Preferably, a golf ball in accordance to the present inventioncomprises a solid or multiple-layer solid core 12 having an outerdiameter of greater than about 1.50 inches, more preferably 1.550 inchesand most preferably 1.580 inches. Moisture vapor barrier layer 14 ispreferably less than about 0.030 inch thick and cover 16 is a urethanecover with sufficient thickness to produce a 1.680 inch diameter golfball. Golf balls were produced in accordance to the preferred dimensionsand formulation discussed above. More specifically, cores with 1.550inch diameter were produced with reduced specific gravity fillers toyield a core specific gravity of about 1.05. Thin sheets of moisturevapor barrier stock material with specific gravity of about 1.50 wereplaced around the core. Sub-assemblies of core and stock werecompression molded for about 30 minutes at about 330° F. Thesesub-assemblies were compared against control cores without the moisturevapor barrier layer. The following results were obtained. Moment of CORDiameter Compression Hardness Inertia (at 125 COR (inch) (PGA) (Shore D)(g · cm²) ft/sec) Slope Core 1.550 77 46 N/A 0.807 −.00105 1.550 inchCore with Thin 1.620 77 36 71.6 0.808 −.00116 Moisture Barrier LayerControl Core 1.592 72 45 66.1 0.796 −.00112 1.590 inch

[0037] The cores with the thin moisture barrier layer and the controlcores were exposed to environments of about 100% humidity at 110° F. forone week (simulating an exposure of 6 weeks at room temperature). The100% humidity environment was achieved by placing a water container inthe oven. The results are as follows: Change in Weight After 1 % Changein Weight After 1 Week in Oven Week in Oven (Simulating 6 Weeks at(Simulating 6 Weeks at Room Temperature) Room Temperature) Control Coresat 100% Humidity +0.76 gram +1.39% Core with Thin Moisture Barrier +0.15gram +0.26% Layer at 100% Humidity

[0038] Hence, the results above show that golf balls made in accordanceto the above invention show a significant gain in moment of inertia overthe control cores (71.6 g·cm² as compared to 66.1 g·cm²) and significantdecrease in moisture absorption (0.15 gram as compared to 0.76 gram).The difference in specific gravity between the core 12 and the moisturevapor barrier layer 14 can be as high as 0.45 or higher. In accordanceto one aspect of the invention, the Shore D hardness values for the coreand moisture vapor barrier sub-assemblies have been measured less thanabout 50 and more specifically in the range of about 30-40.Alternatively, according to other aspects of the invention, the moisturebarrier sub-assemblies may have Shore D hardness value of greater than50, when more rigid materials are used to construct the moisture vaporbarrier layer 14.

[0039] In accordance to a preferred embodiment of the invention, a golfball with a solid PBD core with the thin moisture barrier layer,discussed immediately above, is covered by a thermoset urethane coverhaving a thickness from about 0.10 to about 0.080 inch, so long as thediameter of the ball does not exceed the USGA limit. While a thin coverhaving a thickness from about 0.010 to 0.040 inch is preferred for highswing speed players, a thicker cover having a thickness from about 0.040to 0.080 inch and, more preferably, 0.050-0.070 inch may be employed.The use of this relatively thick thermoset urethane in this embodimentis advantageous for players with moderate swing speeds. These playerswill benefit from a high energy, large PBD core for distance off the teeand more spin, feel and playability for greenside play from therelatively thick thermoset urethane cover, without the moisturepenetration problem normally associated with urethane covered, PBD coregolf balls.

[0040] In accordance to another aspect of the present invention, theintermediate moisture vapor barrier layer 14 may be made from othersuitable materials including (i) multi-layer thermoplastic films, (ii)blends of ionomers, polyvinyl alcohol copolymer and polyamides, and(iii) dispersions of acid salts of polyetheramines, among others.

[0041] Suitable multi-layer thermoplastic films include polypropylenefilms, which have been metallized or coated with PVDC and specificallymodified polyester films such as those described in U.S. Pat. No.6,200,511. The disclosure of the '511 patent is hereby incorporatedherein by reference in its entirety. These multi-layer films preferablyinclude a base layer of thermoplastic polyester and have at least oneouter layer. The base thermoplastic polyester layer is preferablypolyethylene teraphthalate (PET), polybutylene teraphthalate (PBT),polyethylene naphthalate (PEN), polycyclohexanedimethylene teraphthalate(PCDT), or polyethylene naphthalate bibenzoate (PENBB), among others.The outer layer is preferably composed of one or more copolyestersprepared from dicarboxylic acids, and diols or its derivatives, wherethe dicarboxylic acid is composed of a mixture of at least 35 mol %2,6-naphthalate units, up to 44 mol % of teraphthalate units, and 1-20mol % of isophthalate units and from 0-20 mol % of an aromaticdicarboxylic acid, which has been substituted with an alkali metal sulfogroup, among others. Other suitable modified polyesters are disclosed inU.S. Pat. No. 5,506,014. The '014 patent is incorporated herein byreference in its entirety.

[0042] Other suitable multi-layer thermoplastic films include films witha polyolefin base layer such as polyethylene (PE), polypropolene (PP),ionomer, metallocene, etc. and an outer coating layer made from PVDC orethylene vinyl alcohol (EVOH). Other suitable base layers includepolyamide, polyester, polyurethane, polyvinyl chloride (PVC) or anymaterials found in columns 4-6 of the '100 patent, previouslyincorporated by reference. Additionally, other multi-layer polyolefinfilms including a base layer of PP and a non-heat sealable outer layercontaining silicon oxide, such as those disclosed in U.S. Pat. No.5,468,527 and references cited therein. The '527 patent and referencescited therein are incorporated herein by reference in their entirety.

[0043] As stated above, suitable blends of ionomers, polyvinyl alcoholcopolymer and polyamides include a thermoplastic resin compositioncomprising EVOH, ionomer and a polyamide. This composition is suitablefor use as the intermediate moisture vapor barrier layer 14, as well asa coating on the outside of cover 16. A preferred composition comprisesabout 25% or more of an ionomer, about 25% or more of a polyvinylalcohol copolymer and 1-50% polyamide. Examples of suitable compositionsare disclosed in U.S. Pat. No. 6,011,115 and references cited therein.The '115 patent and references cited therein are incorporated by hereinby reference in their entirety.

[0044] Also, suitable dispersions of acid salts of polyetheramines foruse as the intermediate moisture vapor barrier layer 14, as well as acoating on the outside of cover 16, include stable aqueous dispersionsof an acid salt of a polyetheramine prepared by at least partiallyneutralizing the polyetheramine with an acid as disclosed in U.S. Pat.No. 6,180,715. The disclosure of the '715 patent is incorporated byreference in its entirety.

[0045] In accordance to yet another aspect of the invention, as shown inFIG. 3 golf ball 20 may have multiple layer core 12 a, 12 b and 12 c,surrounded by intermediate layer 14 and dimpled cover 16. Core layers 12b and 12 c may be an integral solid layer or discrete layers molded oneach other. Alternatively, both outer core layers 12 b and 12 c could bewound layers, or one of these two layers may be a wound layer.

[0046] In another preferred embodiment, core layers 12 b and 12 c arewound layers that are chemically, physically or mechanically distinctfrom each other. In this embodiment, inner spherical core 12 a may be asingle-layer solid center, multi-layer core or a liquid filled core.Inner spherical core 12 a can be constructed from the suitable corematerials discussed above, and preferably has a diameter from about 0.5to about 1.50 inch. Wound layer 12 b may be made from various threadsincluding, but not limited to, natural rubber, polyether urea (sold asLYCRA® by DuPont), polyester urea, polyester block copolymers (sold asHYTREL® by DuPont), polyethylene, polyamide, polyketon, poly(p-phenylene terephthalamide) (sold as KEVLAR® by DuPont), polyisoprene,among others. Wound layer 12 c may be made from the same suitablethreads listed immediately above, except that wound layers 12 b and 12 cshould be made from different threads.

[0047] An advantage of this preferred embodiment is that the abovelisted suitable threads have different properties, such as density,diameter, elasticity, tensile strengths, etc. Hence, wound layers 12 band 12 c may be wound at different tensions. One layer may be morecompact or more tightly packed than the other layer when one thread hasa smaller diameter than the other, thereby creating a gradient of adesired property for the golf ball. For example, surrounding a woundlayer of highly tensioned polyisoprene thread layer with polyether ureathread layer creates a hard-soft gradient in the core. On the otherhand, surrounding a polyisoprene thread layer with a high modulus layersuch as KEVLAR® creates a soft-hard gradient.

[0048] Advantageously, the intermediate moisture vapor barrier layer 14may surround one or both of the wound layers 12 b and 12 c to minimizemoisture from penetrating into the innermost core 12 a and the woundlayers, especially when one or both of the wound layers or the innermostcore are made from a rubber or polybutadiene material or from othermaterials that are degradable by moisture.

[0049] In accordance to another aspect of the invention, as bestillustrated in FIG. 4, golf ball 30 may have multiple layer core 12 a,12 b and 12 c surrounded by intermediate layer 14, similar to golf ball20, discussed above. Golf ball 30 also has outer dimpled layer 16 a andan inner cover layer 16 b, wherein inner cover 16 b may be a wound layeror a hoop stress layer. Alternatively, as illustrated in FIG. 5, golfball 40 may have a liquid filled center core 12 a, surrounded by a solidinner core layer 12 b, which is surrounded by a solid or wound innercore layer 12 c. Intermediate layer 14, as discussed above, preferablysurrounds inner core layers 12 a, 12 b and 12 c. Cover 16 again may havedimpled outer cover 16 a and inner cover layer 16 b. An optionalintermediate layer 42 may also be provided, which could be solid orwound. Where a liquid core is used, the moisture vapor barrier layer mayserve the added function of preventing moisture vapor from exiting theliquid core to the atmosphere.

[0050] Suitable fluids usable in the liquid filled cores in accordancewith their specific gravities include air, aqueous solutions, liquids,gels, foams, hot-melts, other fluid materials and combinations thereof.Examples of suitable liquids include either solutions such as salt inwater, corn syrup, salt in water and corn syrup, glycol and water oroils. The liquid can further include pastes, colloidal suspensions, suchas clay, barytes, water or other liquid, or salt in water/glycolmixtures. Examples of suitable gels include water gelatin gels,hydrogels, water/methyl cellulose gels and gels comprised of copolymerrubber based materials such a styrene-butadiene-styrene rubber andparaffinic and/or naphthenic oil. Examples of suitable melts includewaxes and hot melts. Hot-melts are materials, which at or about normalroom temperatures are solid but at elevated temperatures become liquid.A high melting temperature is desirable since the liquid core is heatedto high temperatures during the molding of the inner core, outer core,and the cover. Alternatively, the liquid can be a selective reactiveliquid system, which combines to form a solid. Examples of suitablereactive liquids are silicate gels, agar gels, peroxide cured polyesterresins, two part epoxy resin systems, peroxide cured liquidpolybutadiene rubber compositions, reactive polyurethanes, silicones andpolyesters. Additionally, suitable fluids also include low specificgravity liquid such as SAE 10 oil, SAE 30 oil, methanol, ethanol,ammonia, etc., or a high specific gravity liquid such as glycerin orcarbon tetrachloride.

[0051] Alternatively, as illustrated in FIG. 6, golf ball 50 maycomprise multiple intermediate layers 14 a, 14 b and 14 c, which havesimilar construction as intermediate layer 14 discussed above. As shown,intermediate layer 14 a surrounds inner cores 12 a and 12 b;intermediate layer 14 b surrounds layer 12 c; and intermediate layer 14c surrounds optional intermediate layer 42. Advantageously, eachintermediate layer protects a preselected portion of the core of thegolf ball, such that if moisture vapor penetrates an outer moisturevapor barrier layer, the interior layers remain protected by the innermoisture vapor barrier layers.

[0052] In accordance to another aspect of the invention, the moisturevapor barrier layer 14 may be made by a number of methods. Non-limitingexamples include, but are not limited to, the following methods: (1)Pre-formed semi-cured shells. A quantity of mixed stock of the preferredmoisture vapor barrier material is placed into a compression mold andmolded under sufficient pressure, temperature and time to producesemi-cured, semi-rigid half-shells. The half-shells are then placearound a core (solid or wound) and the sub-assembly is cured in anothercompression molding machine to complete the curing process and to reachthe desirable size. A cover is then formed on the sub-assembly by anyknown method to complete the fabrication of the ball; (2) Sheet stockand vacuum. Thin sheets of the mixed stock of the preferred moisturevapor barrier material are placed on the upper and lower platens of acompression-molded press. Suction force from a vacuum keeps the sheetstight against the mold cavities. A core (solid or wound) is placed inthe bottom cavity above the vacuumed sheet. The sub-assembly is thencured in a compression molding press to cure the sub-assembly and toachieve the desirable size. A cover is then formed on the sub-assemblyby any known method to complete the fabrication of the ball; and (3)Rubber injection molding. Mixed stock of the preferred moisture vaporbarrier material is fed into an injection molding barrel and screw. Thestock is then injected through a nozzle into a mold cavity and surroundsa core (solid or wound). The sub-assembly is then heated under pressureto cure the sub-assembly and to achieve the desirable size. A cover isthen formed on the sub-assembly by any known method to complete thefabrication of the ball.

[0053] Other suitable manufacturing techniques include spraying,dipping, vacuum deposition, reaction injection molding, among others.The moisture vapor barrier layer 14 may also be made by a castingmethod, if the selected moisture barrier material is a castablematerial, including, but are not limited to, epoxy, silicones, acrylics,IPN's, polyurethane-ionomers, polyureas and polyesters. Furthermore, anynumber of fillers, fibers, flakes such as mica, metal, ceramic,graphite, etc., can be added the castable materials to make them moreimpervious to water vapor. A known two-pack casting method, such as theone disclosed in U.S. Pat. No. 5,897,884, can also be used. The '884patent is hereby incorporated by reference in its entirety. Generally,in a two-pack casting method, the polyurethane material is formed by areaction between polyurethane prepolymer and a curing agent. Thepolyurethane prepolymer itself is formed by a reaction between a polyoland a diisocyanate. A catalyst may be employed to promote the reactionbetween the curing agent and the polyurethane prepolymer. The mixing andcasting sequence and the timing are controlled as discussed in the '884patent. Furthermore, the mixed materials have a relatively limited shelflife due to the reaction of the isocyanate group with the othercomponents after mixing. Precisely measured ratio of the components isdesirable, because off-ratio mixing yields less desirable components.

[0054] In accordance to another aspect of the invention, a simplifiedcasting method to produce the moisture vapor barrier layer 14 isprovided. More particularly, this simplified method is usable to makeany castable components of the golf ball, including the moisture vaporbarrier layer, any intermediate layer, the innermost core or any portionof the cover. An example of this application is casting a blockedurethane moisture vapor barrier layer or any other layer onto a golfball core.

[0055] A preferred embodiment of this method uses uretdiones or blockedisocyanates to form a single-pack urethane component. The single-packblocked isocyanate system, which preferably comprises isocyanatecombined with an amine or poloyl, is advantageously stable at roomtemperature. The application of heat causes the isocyanate to becomeunblocked or to react to form a urethane. No mixing or dynamicallycontrolling the ratios of the components is required.

[0056] Uretdione castable materials can be pre-formulated as asingle-pack system without premature reaction. The mixed single-packmaterial can be directly injected or poured into a mold, avoidingmetering and mixing of multiple components. Parts can be made utilizingviscous or solid materials that previously could not be used withtraditional two-pack systems. Advantageously, uretdiones and blockedisocyanates when combined with suitable reactive components can bemilled into rubber stock for use with other manufacturing techniques,discussed above.

[0057] A non-limiting example of a single-pack system in accordance tothe present invention is as follows. Finely ground uretdione isdispersed in a liquid polyol or polyamine in combination with a tincatalyst and cyclic amidine catalyst. A slurry is created. The slurrymixture is poured into a suitable golf ball mold to make the requiredpart, e.g., core, intermediate layer or cover. The mold is then heatedto reach the predetermined deblocking temperature of about 150-180° C.,and the reaction is allowed sufficient time to complete. The curedcomponent then can be removed from the mold for further processing, ifnecessary.

[0058] In another example, 3,5 dimethylpyrazole (DMP) blocked-IPDI isused in place of the uretdione in the above example. The mold is thenheated to the deblocking temperature of about 140-160° C., and thereaction is allowed sufficient time to complete. Non-limiting chemicalstructures of the single-pack system are shown below:

[0059] Formation of uretdiones:

[0060] Preferred chemical structure of polyuretdione cross-linker:

[0061] The preferred hardeners are uretdiones or a blocked isocyanates,where the blocking agent remains in the component as a solid once cast,such as DMP or triazole blocked isocyanates. The structures of thepreferred blocking agents are:

[0062] As stated above, the single-pack casting method can also be usedto produce the innermost core, any intermediate layer or any otherportion of the golf ball.

[0063] While various descriptions of the present invention are describedabove, it is understood that the various features of the presentinvention can be used singly or in combination thereof. Therefore, thisinvention is not to be limited to the specifically preferred embodimentsdepicted therein.

What is claimed is:
 1. A method of casting a portion of a golf ballcomprising the steps of: providing a single component that is blockedand stable at a first predetermined temperature and becomes unblocked ata second predetermined temperature, wherein said second predeterminedtemperature is higher than the first predetermined temperature; andreacting said single component at the second predetermined temperatureto form the surrounding layer.
 2. The method of claim 1, wherein thesingle component is an uretdione or blocked isocyanate material.
 3. Themethod of claim 1, wherein the step of providing the single componentcomprises the step of combining isocyanate with an amine or poloyl. 4.The method of claim 1, wherein the step of providing the singlecomponent comprises the steps of: grinding a uretdione; dispersing theground uretdione in a liquid of polyol or polyamine; combining with atleast one catalyst to create a slurry; and pouring the slurry into amold and heating the mold to the second predetermined temperature. 5.The method of claim 4, wherein the second predetermined temperature isin the range of about 150 to about 180° C.
 6. The method of claim 1,wherein the step of providing the single component comprises the stepsof: grinding 3,5 dimethylpyrazole blocked-IPDI; dispersing the ground3,5 dimethylpyrazole blocked-IPDI in a liquid of polyol or polyamine;combining with at least one catalyst to create a slurry; and pouring theslurry into a mold and heating the mold to the second predeterminedtemperature.
 7. The method of claim 1, wherein the second predeterminedtemperature is in the range of about 140 to about 160° C.
 8. The methodof claim 1, wherein the portion is an intermediate layer.
 9. The methodof claim 8, wherein the intermediate layer is a vapor barrier layer. 10.The method of claim 1, wherein the portion is a cover.
 11. The method ofclaim 10, wherein the cover is a vapor barrier layer.
 12. The method ofclaim 1, wherein the portion is a core.
 13. A method of casting aportion of a golf ball comprising the steps of: grinding a uretdionehaving a first predetermined temperature at which the uretdione isblocked; dispersing the ground uretdione in a liquid of polyol orpolyamine; combining with at least one catalyst to create a slurry; andpouring the slurry into a mold and heating the mold to a secondpredetermined temperature sufficient to cause the uretdione to becomeunblocked, the second temperature being higher than the firstpredetermined temperature, to form a surrounding layer.